The present invention relates to a technique for viewing depth of field images. More particularly, the present invention relates to a curved prismatic screen which takes advantage of depth cues in a flat-type image to permit a viewer to see most of the depth of field elements that exist in the real image. Furthermore, the present invention relates to a technique for reducing grain in an image and providing increased contrast and improved clarity in the image.
There currently are a number of optically or electronically guided depth of field systems for still photography, television, film, video and the like. These current systems are typically based on human eye stereopsis rules whereby two separate images, taken at the distance of the eyes, are separately provided to the respective eyes of the viewer. Examples of these types of systems are described below in connection with FIGS. 1-4.
Referring to FIG. 1, one known technique for providing a stereoscopic image utilizes a stereo pair of photographic images a and a' and a pair of half lenses 1 and 1'. In operation, the half lenses 1 and 1' cause an observer to view a fused stereoscopic image c which includes apparent depth information. As a result, a viewer will perceive a three-dimensional effect in the fused image.
FIG. 2 illustrates a system useful for providing three-dimensional images for a motion picture or the like. A pair of film images a and a' are projected by lenses 3 and 3' through polarizing light filters 5 and 5', respectively, onto a metallic nondepolarizing screen 7. A viewer wears appropriate polarizing glasses 9, which allow each of the viewers' eyes to see the corresponding film image a or a'. As a result, a fused stereoscopic apparent image c is "seen" by the viewer for a three-dimensional effect.
A third known device for producing stereoscopic images is illustrated in FIG. 3. A stereo pair of video cameras 11 and 11' converge at a point f to provide video camera images a and a', respectively, for simultaneous display on video screen 15. A pair of shutters 17 and 17' allow alternate viewing of the video display by the viewer. Only one eye is exposed to the image at any given moment. As a result, the viewer perceives a three-dimensional effect in the image.
A number of techniques for producing stereoscopic images are described in patent literature. For example, PCT Application No. WO 81/01201 to Shanks describes a system which produces a distorted plane image of a scene and causes observation of the distorted image on a saddle-shaped surface to give a three-dimensional presentation of the scene. Other techniques are described, for example, in U.S. Pat. No. 2,889,739 to Moore; U.S. Pat. No. 2,891,444 to Ewald; U.S. Pat. No. 4,078,854 to Yano; U.S. Pat. No. 4,158,481 to Hoyer; U.S. Pat. No. 4,621,897 to Bonnet; U.S. Pat. Nos. 4,772,094 and 4,871,233 to Sheiman; and U.S. Pat. No. 4,927,238 to Green et al.
Each of the foregoing techniques is based on stereopsis, three-dimensional depth rules. Referring now to FIG. 4, the eyes of a viewer v are converged at a point b. As an example of depth rules, an object placed closer than convergence point b appear to be shifted left at point c. Objects placed further than convergence point b appear shifted right at point d.
Although existing three-dimensional imaging systems simulate stereopsis of the eyes fairly effectively, they require a special camera attachment, a two camera arrangement, or other means, to provide two images for a stereo pair. The stereo pair images require a device to separate them during viewing so that each eye of the viewer can see only one image of the stereo pair.
Due to the need for special camera systems and other equipment, shooting and recording images in three-dimensions is difficult, and viewing is restricted by the requirement of special glasses, eye shutters or similar devices. Three dimensional viewing systems are complicated, are commonly considered to be a gimmick, cause eye strain during viewing, and are expensive. Accordingly, they have not been accepted by the public or commercial film and video markets for any sustained period of time.